DNR says VHS is here to stay

Published 8:00 pm, Wednesday, April 11, 2007

DNR fisheries managers and researchers will deal as best they can with Viral Hemorrhagic Septicemia (VHS), which caused fish kills in the last several years in southeast Michigan and northern Lake Huron.

But they're under no illusions.

"We'll never get rid of it," said Gary Whelan, supervisor of Michigan's fish hatchery system, in a phone interview last week.

"It's ours forever. We're stuck with it. We will learn to manage around it."

In the short term, that means that no walleye eggs are being collected from the Tittabawassee River this spring, and there will be no rearing and planting of walleyes, northern pike or muskellunge in Michigan.

VHS has not been detected in Saginaw Bay walleyes, which fuel the spawning run up the Tittabawassee. But it's between two known areas of infection, and considered very likely to be hit with the malady.

Too likely for hatcheries to take a chance. "We can't put our extremely expensive assets at risk," said Whelan.

It takes several weeks for labs to detect VHS, by which time eggs could have contaminated hatcheries. That would require extermination of all the fish in the hatchery, plus its shutdown for decontamination - a loss DNR officials say could cost the state $40 million or more.

There would also be the risk of introducing VHS to inland and other waters, something managers want to avoid.

And so, until techniques have been developed to deal with VHS in eggs - or at least to rapidly test eggs for the disease - rearing of walleyes, pike and muskies has been halted.

DNR crews have temporarily stunned thousands of walleyes, tagging them with metal bands and releasing them so that anglers can report catches to better define local walleye lifestyles.

They also captured 60 walleyes to be sent to a lab at Michigan State University where their health, including VHS status, will be determined. This multi-year program began before VHS came on the scene, probably brought up the St. Lawrence Seaway in the ballast of freighters.

But they collected no eggs. Not here, anyway.

The memory is too fresh from last year, when chinook salmon harvested at a weir on the Swan River near Rogers City tested positive for VHS, after eggs collected there were already in the hatchery system.

"The fish from which we took eggs were probably (VHS-)positive," said Whelan.

Fisheries officials held their breath, waiting to see if their now-standard double-disinfecting technique, instituted to reduce bacterial kidney disease (BKD) in chinook salmon, worked against the newcomer disease. To their relief, it did. "There's been no sign of VHS," he said.

And so, they know it works with trout and salmon. But coolwater species such as northern pike and walleyes are different in many ways, and one can't assume it will work with them, too.

That's why, ironically, Whelan is hoping that walleyes collected from the Huron River this spring will test positive for VHS. Their eggs are being collected - and kept separate from the hatchery systems - double-disinfected with an antibiotic, and incubated.

The goal? Disease-free fry produced from infected fish.

"If we determine that our disinfection techniques work (with coolwater fish), then we're back in business and producing fish next year," Whelan said.

And learning to live with another lethal wrinkle in the Great Lakes system.

Sources and release sites for eggs

Walleye eggs are collected from the Tittabawassee River, from the Muskegon River, and from Little Bay de Noc in the Upper Peninsula.

Northern muskellunge eggs come from Hudson Lake and Thornapple Lake.

And pike eggs and milt come from Kent Lake, Little Bay de Noc, and Sanford Lake.

The DNR stocks walleyes at about 120 sites, muskies at 15, and northern pike at nine.